As the week began, Prime Minister Ariel Sharon resolved to confront his old friend Rehavam Ze’evi, minister of tourism and leader of the National Unity faction, who had been urging the premier to get much tougher with the Palestinians.

Sharon had just ordered the army out of Palestinian sections of the West Bank city of Hebron, occupied a week earlier to prevent gunmen from shooting at Jewish residents. In response, Ze’evi and his seven-member National Unity-Israel, Our Home bloc threatened to secede from the government.

Sharon told Ze’evi from the Knesset podium Monday that if he left the coalition, “You’ll make Arafat’s day.”

Ze’evi and his colleague in the Cabinet, Avigdor Lieberman, did, indeed, leave

Less than 48 hours later — the time needed for his resignation to take effect — Ze’evi was dead, killed by a Palestinian assassin’s bullet in a Jerusalem hotel corridor.

As the week ended, Sharon still confronted the same dilemma, only this time with more poignancy.

The murdered man’s colleagues — who rescinded the resignation and said they would reconsider after the mourning week — along with others on the right of Sharon’s unity government were urging the premier to ratchet up Israel’s military measures against the Palestinians.

Some ministers were explicitly demanding that the Israeli army target Palestinian political leaders in response to Ze’evi’s killing.

From the other wing of his government, Sharon heard voices questioning the wisdom of the “targeted killings” policy. The Popular Front for the Liberation of Palestine claimed responsibility for Ze’evi’s slaying — in revenge, the group said, for the Aug. 27 killing of the PFLP secretary-general, Mustafa Zibri.

Following a string of terror attacks in Israel carried out by the PFLP, an Israeli helicopter gunship fired two missiles into the window of the Ramallah office where Zibri worked, killing him and leaving the rest of the building intact.

Over the phone, from Washington and from China, where Secretary of State Colin Powell is travelling, world leaders called on Sharon to exercise restraint.

Palestinian Authority President Yasser Arafat, also facing U.S. pressure, telephoned Foreign Minister Shimon Peres late Wednesday to say he was cracking down on the PFLP. The organization’s spokesman in Bethlehem, Ali Jeradat, who was the first to take public credit for the killing of Ze’evi, has been arrested, Arafat said, along with two others.

“Arrest them all,” Peres replied somberly, “or else one pistol shot will have set fire to this entire region.”

By mid-evening, Israel Television was reporting that Jeradat was free again.

Earlier, Sharon told the Knesset in a special mourning session that Arafat “and Arafat alone” was responsible for the assassination.

He had done “nothing serious” to curb terrorism, Sharon said, despite his pretense to the world that he had taken action. By doing nothing, he had in effect given the go-ahead for attacks such as the one that killed Ze’evi, Sharon implied.

Sharon did not explicitly threaten to move against the Palestinian Authority chairman — as Ze’evi had urged repeatedly in recent months. But there was an ominous undertone in his words.

Ze’evi’s killing clearly has heightened tensions and dangers in the region. Yet it could, paradoxically, enhance prospects for an end to the violence and a return to peace negotiations.

If Arafat, under American prodding and fearful of massive Israeli retaliation, finally takes convincing action against terrorist elements — and if Sharon again, as he did at the beginning of the week, chooses moderation — it could add to the incremental momentum toward a stable cease-fire and new talks.

Israel said Wednesday it would cut off further diplomatic contacts with the Palestinians until there was a firm cease- fire.

But the Americans are certain not to be deterred by that initial reaction. And, despite his fury and his determination to strike back, close aides say Sharon will be mindful of Washington’s call for restraint when deciding on reprisal actions.

If the military response is relatively moderate, and if the Americans press on with their peacemaking efforts, then presumably Ze’evi’s seven-man faction — which consists of his National Unity Party and Lieberman’s Israel, Our Home immigrant party — will quit the government after all. That would dangerously weaken Sharon’s survival prospects.

The prime minister still would have a comfortable margin of 16 seats in the 120-person Knesset, but looks can deceive.

If Shas, the Sephardic Orthodox party that has 17 seats and a largely hawkish electorate, were to defect, Sharon would lose his majority. And Shas will be under constant pressure to do so, because it is competing for some voters with the National Religious Party, which is not in the coalition.

Similarly, Yisrael Ba’Aliyah, a smaller coalition party that also serves the Russian immigrant community, will be vying for voters with Israel, Our Home, which by that time would be in the opposition.

However, if he veers rightward to keep those parties Sharon risks losing Labor, which itself is subject to constant sniping from the dovish Meretz Party and is divided internally over its junior role in Sharon’s government.

And in the wings, Benjamin Netanyahu is waiting to challenge Sharon for leadership of the national camp. Together, those challenges mean that the decision of Ze’evi’s faction — and Sharon’s choice of steps now — could have serious repercussions for both Israel and the Palestinians.

Meanwhile, as with Yitzhak Rabin’s killing six years ago, the assassination has raised questions about the efficacy of the Shin Bet’s bodyguard department.

Avi Dichter, director of the Shin Bet, issued a statement Wednesday accepting full responsibility for the failure to protect Ze’evi. In fact, not all Israeli ministers are guarded at all times, and the tourism minister had not had guards with him in the hotel, where he often stayed when in Jerusalem.

Ze’evi, moreover, was a particularly obstinate client for the Shin Bet. He often bristled at protection even when it was available, arguing that he deserved no greater security than any ordinary citizen.

Still, the Shin Bet has set up an internal inquiry board, and its work could be followed by an examination by an external panel if the results are unsatisfactory. Moreover, the Shin Bet is reconsidering its protection procedures and has attached security details to all ministers for the time being.

Sharon Wednesday night issued a statement voicing his full confidence in Dichter.

On the personal level, Ze’evi’s tragic death seemed to bring out the best in Israeli politics Wednesday as the Knesset united to mourn him.

Despite his far-right views, “Gandhi,” as he was universally known since his days in prestate Palestine’s Jewish fighting forces, was well-liked across the board.

“He knew how to respect a fellow human being,” said Abdulmalik Dehamshe, an Arab Knesset member and bitter ideological foe of Ze’evi.

Yossi Sarid, leader of the opposition, eulogized Ze’evi from the podium as “an opponent who was a friend,” recalling “moments of real closeness” that had spanned the political distance between them.